In this work, H13 tool steel was prepared with different oxidation treatments to investigate the effects of oxidation temperature and soaking time. In order to improve erosion and corrosion resistance, this study tested with oxidation temperatures of 560°C, 580°C, and 600°C, and oxidation soaking times of 1 h, 2 h, and 3 h, respectively. Experimental results showed that the oxidation treatment at 600°C and for 3 h is the optimum process. The average thickness of the oxide layer was 9.2 mm. It showed that the oxide layer (Fe 3 O 4 ) can protect and improve the aluminum erosion of H13 steel. The specimens that underwent the oxidative procedure were proven to effectively reduce the ratio of Al-Fe-Si compounds during erosion tests of A380 alloy solution. In addition, the results showed that the oxide layer can enhance polarization resistance, and quickly generate a passivation layer to increase the ability of corrosion resistance.KEY WORDS: H13 tool steel; erosion; corrosion; oxidation; A380 alloy. 569© 2010 ISIJ in order to enhance the erosion rate and weight loss. After removing the aluminum, specimens were cleaned with NaOH to remove any oxide or other residue. The weight loss percentage of erosion test is calculated as follows:Weight loss (%)ϭ(IWϪAW)/IWϫ100 IW is the initial weight, and AW is the weight after erosion test.Corrosion potential analysis adopted three electrodes method. Reference electrode was saturated with silver-silver chloride electrode, auxiliary electrode was a Platinum electrode, and working electrode was connected to the testing specimens. The contact area of specimen was 2.01 cm 2 . Meanwhile, the corrosive solvent used 3.5 wt% NaCl, and was kept at room temperature. The main parameters of corrosion testing included: scanning speed of 0.5 mV s Ϫ1, initial potential of Ϫ1.5 V, and the final potential of 0.5 V. The polarization curve was obtained by Corr-View software for analysis, and compared with different oxidation parameters of the corrosion potential (E corr ) and corrosion current (I corr ). Finally, the polarization resistances (R p ) of different oxidation treatments for AISI H13 tool steel were compared. To evaluate the improvement in erosion and corrosion resistance of AISI H13 tool steel via different oxidation processes, erosion and corrosion tests, XRD and EDS, and microstructure inspections were performed. Figure 3 shows the XRD patterns of H13 tool steel after 560°C 1 h, 2 h, and 3 h of oxidation treatment. As seen, the strongest peak is the original a-Fe structure, in addition, there are two other different crystal structures, Obviously, at the same temperature and different soaking times of oxidation treatment, XRD analysis indicated that two different kinds of oxide layers were provided after oxidation treatments, which are the crystal structures of Fe 3 O 4 and Fe 2 O 3 . The intensity of the original a-Fe gradually decreased as the soaking time of oxidation increased, indicating that increasing the soaking time of oxidation would reduce the proportion of the a-Fe structur...
In order to effectively improve erosion resistance and evaluate the effects of an oxy layer on AISI H13 tool steel after the oxynitriding process, this study used three different nitriding surface treatments, namely oxynitriding process 1 (using air), oxynitriding process 2 (using steam) and normal gas nitride. To evaluate the effects of microstructure and the erosion resistance of AISI H13 tool steel after different nitride processes, evaluated micro hardness, erosion tests and SEM microstructure inspections were conducted. Experimental results showed that the oxide layer can protect and improve the aluminum erosion for AISI H13 tool steel. Erosion tests of 2 and 4 h for oxynitriding process 1 could produce a thicker and complex oxide layer, which has higher hardness (HV 1021.9) and optimal weight loss (0.16 %). This procedure is proven to effectively reduce the ratio of Al-Fe-Si compounds during the A380 alloy erosion test.KEY WORDS: erosion resistance; AISI H13 tool steel; oxynitriding; A380 alloy. 421© 2009 ISIJ erosion test as shown in Fig. 1(b). The specimen was then dipped in aluminum alloy A380 for melting and maintained at 1 023 K. The rotational speed of the specimen was kept at 50 rpm. The dip time was 2 and 4 h for specimens to evaluate the erosion resistance and weight loss. After removing the aluminum, the specimens were cleaned with NaOH to remove oxide or other residues. The weight loss percentage of the erosion test was calculated as follows:IW is the initial weight and AW is the weight of after erosion test. In the experiment, three different kinds of surface treatments were: 1) normal gas nitriding: at temperature of 843 K for 1 h; 2) oxynitriding process 1: gas nitriding was carried out at temperature of 843 K for 1 h, and air oxidation at 823 K for 3 h; 3) oxynitriding process 2: gas nitriding was carried out at temperature of 803 K for 1 h, and steam oxidation at 798 K for 1 h. To evaluate the effects of erosion resistance on AISI H13 tool steel by nitriding process, erosion test, surface hardness and microstructure inspections were performed. Microhardness tests were measured by HV with loading of 200 g, which complied with the CNS 2115 Z8004 standard. Results and DiscussionThe microstructure of AISI H13 tool steel substrate obtained after quenching and tempering processes is shown in Fig. 2. This is the typical microstructure obtained through commercial heat treatment, which comprises the structure of tempered martensite and proeutectoid carbides. Figure 3 shows the microhardness test of AISI H13 tool steel after gas nitriding and different oxynitriding treatments. Gas nitriding was done with ammonia, decomposition NH 3 was used to dilute the ammonia so that it was not too aggressive. Normally, pure decomposition NH 3 is used to reduce the compound layer (white layer). Both carbon content and alloying additions raise surface hardness, thereby enhancing wear resistance. The actual hardness of the compound layer is usually substantially higher. However, a better thickness of the compound l...
The aim of this paper was to study the effects of die life through shot peening treatments on AISI H13 steel, and tests were performed to study the influential parameters of the shot peening process. To evaluate the effects of microstructure and the die life of AISI H13 steel after steel shot peening processes, we conducted and evaluated roughness tests, micro hardness and wear tests, and SEM microstructure inspections. The shot peening process was conducted under a pneumatic peening machine. Experimental results showed that 0.3 mm steel shots and 30 minutes at 451 kPa of shot peening treatment was optimum for AISI H13 steel for improving wear resistance and the die life of steel. It enhanced the surface hardness to HV 561 and extended ability of the limit wear resistance for AISI H13 steel. Dislocation microstructure emerged on the steel surface by shot peening. In particular, this technology has been successfully applied to forging die, and is able to improve and extend the die life of steel 2 to 3 times.
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